Constructing multifunctional deep-blue emitters with weak charge transfer excited state for high-performance non-doped blue OLEDs and single-emissive-layer hybrid white OLEDs

Deep-blue emitter with high photoluminescence efficiency(PLQY)is highly desirable in ultra-high definition displays and white solid-state lightings.In this work,two deep-blue phenanthro[9,10]imidazole derivatives,PPIS and PPPIS,with hot exciton property are successfully developed.Compared to PPIS,the embedded phenyl bridge in PPPIS is able to effectively increase the overlap of frontier molecular orbitals.In consequence,PPPIS shows higher oscillator strength and significantly enhanced PLQY.PPPIS also achieves better electroluminescence performance in non-doped device,showing deep-blue emission with Commission International de l’Eclairage(CIE)coordinates of(0.153,0.087)and the maximum external quantum efficiency(EQEmax)of 8.5%with minuscule efficiency roll-off.Meanwhile,when PPPIS serves as the host for phosphor PO-01,high-efficiency orange phosphorescent device is obtained with high EQEmax of 29.8%and negligible efficiency roll-off at 1000 cd/m^(2).Further,efficient single-emissive-layer white device is assembled via utilizing PPPIS as a blue emitter as well as the host for PO-01 simultaneously,providing warm-white emission with CIE coordinates of(0.429,0.433)at 1000 cd/m^(2),the forward-viewing EQEmaxof 27.2%and maximum power efficiency(PEmax)of 80.1 lm/W,respectively.Our studies can establish a viable design strategy for deep-blue emitters in high-performance non-doped blue OLEDs and hybrid WOLEDs.

Utilizing morpholine for purely organic room temperature phosphors

In this article,morpholine,a non-conjugated heterocycle,is embedded intoπsystem to construct single-component organic room temperature phosphorescence(RTP)luminogens.The effect of morpholine on intermolecular interaction,crystal packing modes,and RTP performance is investigated systematically.The experimental and theoretical calculation results illustrate the versatility of morpholine in promoting the n-π*transition and intensifying the intermolecular interactions,which not only enhances the generation of triplet excitons,but also suppresses the nonradiative decay of triplet excitons.Impressively,TMPh containing three morpholine units shows an ultralong lifetime of 1.03 s and a visible afterglow up to 10 s.The unique dual delayed emission and long afterglow property allow potential application of morpholine derivatives in data encryption,and the time-dependent color change of afterglow emission is realized after removing the excitation source,providing a high-level data security.This article provides a new perspective for the design of purely organic RTP system without utilization of metal,or even any heavy atoms.